Shot obturation system for fully telescoped caseless ammunition

ABSTRACT

A tubular propellant charge fully telescoping an igniter tube having a first primer charge affixed in an outwardly facing recess therein and a projectile having a second primer charge affixed to the aft end thereof. The igniter tube has axial openings communicating between the first and second primer charges through which a flash wave caused by the detonation of the first primer charge propagates to detonate the second primer charge. The resulting ignition of the second primer charge advances the projectile so that the fore end thereof obturates the bore of the weapon barrel rapidly and accurately.

United States Patent [191 Plumer Nov. 19, 1974 SHOT OBTURATION SYSTEM FOR FULLY TELESCOPED CASELESS AMMUNITION Inventor: Roy D. Plumer, Santa Barbara,

Calif.

Assignee: General Motors Corporation,

. Detroit, Mich.

Filed: May 15, 1970 Appl. No.: 37,523

U.S. Cl 102/38, 102/45, l02/49.3 Int. Cl. F42b 5/18, F42b 9/16 Field of Search 102/38, DIG. l, 40, 43

References Cited UNITED STATES PATENTS 3/1970 Hensley etal. 102/38 x 9/1970 Harrell 102/38 x Primary Examiner-Robert F. Stahl Attorney, Agent, or Firm-Albert F. Duke [5 7] ABSTRACT A tubular propellant charge fully telescoping an igniter tube having a first primer charge affixed in an outwardly facing recess therein and a projectile having a second primer charge affixed to the aft end thereof. The igniter tube has axial openings communicating between the first and second primer charges through which a flash wave caused by the detonation of the first primer charge propagates to detonate the second primer charge. The resulting ignition of the second primer charge advances the projectile so that the fore end thereof obturates the bore of the weapon barrel rapidly and accurately.

4 Claims, 2 Drawing lFigures SHOT OBTURATION SYSTEM FOR FULLY TELESCOPED CASELESS AMMUNITION This invention relates to caseless fully submerged and telescoped ammunition wherein obturation is caused by primer means affixed to the aft end of the projectile and detonated by the flash wave produced by the detonation of other primer means.

With caseless ammunition, as with other kinds, the projectile must obturate the bore of the barrel both to prevent excessive flow of propellant gas ahead of the projectile and to align the axis of the projectile accurately with the axis of the bore so as to afford firing accuracy and maximum muzzle velocity. However, as the size of caseless rounds increase due to increases in the size of the projectile or the kinetic energy to be imparted to it by the propellant, satisfactory and accurate obturation becomes more difficult to obtain repeatably. With fully telescoped ammunition, the projectile may be advanced to obturate the barrel either by the action of a bolt inserted through the bore of the propellant to first partially eject the projectile into the barrel and then ignite the propellant by igniting a primer on the aft end of the projectile or by utilizing the pressure built up by the propellant gas. With the former approach the rate at which the propellant ignites and builds up pressure is impaired by the fact that the only primer is on the aft end of the projectile which itself is remote with respect to at least one end of the propellant tube. With the latter approach advancement of the projectile into the barrel is slow being determined by the rate that pressure is built up by the burning propellant gases. Also the guidance effected by the bore of the propellant tube on the sides of the propellant is degraded as the burning first deforms and then consumes the tube. Another disadvantage with this approach, one that becomes more pronounced with increased size, is that a significant portion of the propellant gases escape into the barrel ahead of the projectile before obturation thereby wasting a significant portion of the potential energy in the gases that might otherwise be converted into the kinetic energy of the projectile.

Another approach has been to telescope the projectile just partially within the propellant charge and then advance both the propellant charge and projectile by means of a bolt acting on the end of the propellant tube. However, due to the forces required to obturate the projectile into the barrel, the forces applied by the bolt to the propellant tube often deform the latter thereby debilitating not only its burning properties but also the ability of its sides to guide the projectile into the barrel.

For similar sizes, weights, and chemical compositions, caseless rounds of the present invention attain a more rapid and accurate obturation. They utilize a higher proportion of the energy available from the propellant gas; they attain a higher muzzle velocity and firing accuracy; and finally, they obtain such features more repeatedly. Moreover, these features are obtainable with rounds of increasing sizes and without the need for any bolt action to obturate the barrel.

Utilizing the vast difference between the burning rate of the propellant and the propagation rate of a flash wave produced by an explosion, the present invention employs the flash wave and propagation thereof created by the detonation of a first primer charge affixed at one end of the tubular propellant to detonate a sec- 0nd primer charge affixed to the aft end of the projectile also telescoped by the propellant. Upon the detonation of the second primer charge, the latter exerts a net resultant impulse on the projectile and along its axis, causing the projectile to rapidly obturate the barrel in alignment with the axis of the bore thereof. Such accurate obturation is effected, and the sides of the projectile are engraved with the riflings in the barrel, prior to the substantial ignition of the rest of the propellant charge thereby allowing the energy in the propellant gas to be utilized substantially for providing kinetic energy to the projectile.

It is therefore a primary object of the present invention to provide a round of fully telescoped caseless ammunition wherein the flash wave produced by the detonation of a first primer affixed to a tubular propellant charge causes the detonation of a second primer affixed to the end of the telescoped projectile with the result that the projectile rapidly obturates the bore of the barrel and has its axis substantially aligned therewith.

It is a further object of the present invention to provide a round of caseless ammunition of the foregoing type wherein the first primer charge is mounted in a recess at one end of an igniter tube and upon detonation propagates a flash wave through axial openings in the tube to detonate the second primer.

It is a further object of the present invention to provide a round of caseless ammunition of the foregoing type wherein a relay primer is affixed in the igniter tube between the first and second primers and upon being detonated by the flash wave from the first primer rein forces and relays this flash wave to effect detonation of the second primer.

These and other objects of the present invention will be apparent from the discussions below taken in reference with the accompanying drawings wherein:

FIG. 1 illustrates a longitudinal section through a fully submerged round of caseless ammunition made in accordance with the invention, and

FIG. 2 illustrates a longitudinal section through an embodiment of an igniter tube having a relay charge mounted intermediate the ends thereof to relay the shock wave from the first primer charge on the igniter tube to that on the aft end of the projectile.

Referring now to FIG. 1, there is shown a round of fully submerged ammunition 10 comprised of a propellant charge 12 molded to have therethrough an axial bore 14 of sufficient length and diameter to fully telescope and receive therein an igniter tube 16 and a projectile 18. Both tube 16 and projectile 18 are affixed to the sides of the bore 14 by an adhesive compound 20 having sufficient strength to prevent inadvertent ejection of tube 16 or projectile 18 during loading or dropping. A compound suitable for these purposes is nitrocellulose dissolved in either methyl ethyl ketone or acetone mixed with ethyl acetate.

lgniter tube 16 is comprised of a propellant charge similar in composition to that of charge 12 and molded to form a cup-like cylinder having sides 22 defining an inner surface 23 and terminating in a mouth 24 and a radial wall 26. Wall 26 has an outwardly facing pocket 28 therein and an axially extending opening 30 therethrough, the latter providing a channel between pocket 28 and a cavity defined by surface 23. Located in pocket 28 of tube wall 26 is a first primer charge 32 such as crystalline lead styphnate PbC H N O having a density of 3.02 g/cc and a detonation velocity of 5,200 m/sec. Another suitable stab primer is a composition of 40 percent by weight of lead styphnate, 20 percent barium nitrate, 20 percent lead azide, percent antimony sulfate, and 5 percent tetracene. Other primer compositions include lead styphnate mixed with zirconium and appropriate sensitizers as known to those skilled in the art.

The axial thickness of wall 26 as well as the diameter of opening 30 are selected to effect two requirements. The first is that wall 26 must be strong enough to provide a firm support to primer 32 upon the impact thereon of either percussion or stab (friction) firing means. The second requirement is that the size of opening 30 should be sufficient to pass the flash wave created upon the detonation of primer 32 without hindering its propagation velocity.

Projectile 18 has a tapered nose 40, sides 41 and an aft end 42, with the latter located in proximity to mouth 24 of igniter tube 16. Aft end 42 hasa rearward facing cavity 44 defining therein a radially extending surface 46 perpendicular to the longitudinal axis of projectile 18. A second primer charge 48 of composition similar to that described above for primer 32 is secured to surface 46 in cavity 44 by suitable means.

FIG. 2 shows an alternate embodiment of the invention similar to that shown in FIG. 1 but more suitable for use in larger rounds where the distance between the first and second primer means might allow the flash wave to expend itself without reliably detonating the second primer charge. To reduce this possibility, a third primer or relay pellet 50 is affixed to surface 23 of igniter tube 16 by adhesive 21 similar in composition to adhesive 20. Primer 50 is detonated by the flash wave created by the detonation of primer 32 and in turn creates a flash wave reinforcing or otherwise relaying the shock wave from primer 32.

Upon the detonation of primer charge 48 as a result of a flash or shock wave created by the detonation of either primer charge 32 or primer charge 50, the impulse effected on surface 46 by detonating primer 48 first overcomes and breaks adhesive between bore 14 of propellant charge 12 and the projectile sides 41. The remaining portion of the impulse is converted into projectile momentum. This momentum is of sufficient magnitude and duration notjust to rapidly lodge or shoot the projectile 18 into bore 52 of barrel 54 but also to cause the projectile sides 41 to be shaved down slightly by the smaller diameter of bore 52 and to be engraved by riflings 56. The resulting press fit between the projectile sides 41 and the bore 52 and riflings 56 of the barrel 54 then effect the necessary seal required for proper obturation. Another primary obturation requirement, that of proper alignment of the longitudinal axis of projectile 18 with the bore 52, is effected through the cooperation of the axial nature of the thrust force created on surface 46 by detonating primer 48 and by the guidance effects of bores 14 and 52 on the projectile sides 41.

Shortly after such proper obturation, propellant charge 12 is substantially ignited by the spreading effects of the detonation of both primer 32 and also primer 48 to quickly establish a peak pressure for a duration sufficient to impart linear and spinning motion to projectile l8 and attain a suitable muzzle velocity upon leaving bore 52. For instance, it has been found from firings of rounds of 50 caliber caseless ammunition constructed in accordance with the present invention and having a charge to weight ratio of 0.75 that this type of ammunition could be fired repeatedly and accurately, that more than 25 percent of available potential energy was converted into kinetic energy, and that peak chamber pressures of 65,000 psi and muzzle velocities of up to 3,800 fps were obtained.

It will be obvious to those skilled in the art that modifications and changes may be made without departing from my invention. For instance, the cavity 44 on the aft end of the projectile 18 could be eliminated and primer 48 affixed directly to surface 46. Also where manufacturing techniques permit a propellant 12 to be molded form a recess 28 and opening 30, a separate igniter tube could be eliminated.

I therefore aim in the appended claims to cover such modifications and changes as fall within the true scope of my invention. What I claim as new and desire to secure by letters patent of the United States is:

1. In a round of telescoped caseless ammunition:

a. a tubular propellant charge comprised of first and second end portions and an axial bore therebetween, said first end portion having a radial wall with an outwardly extending axial pocket therein and an axial opening communicating between said pocket and said bore;

b. a projectile having nose, side, and aft sections and affixed to said bore at said side section, said sections located within said bore between said first and second end portions; and

c. first and second primer means affixed respectively in said'pocket of said first end portion and to said aft section of said projectile, whereby detonation of said first primer initiates a flash wave that propagates through said axial opening of said pocket and said axial bore of said propellant to detonate said second primer means and whereby the detonation of said second primer means advances said nose section of said projectile beyond said first end portion of said propellant prior to substantial ignition of said propellant.

2. In a round of telescoped caseless ammunition:

a. a tubular propellant charge comprised of first and second end portions and an axial bore therebetween; v

b. an igniter tube affixed within said bore at said first end thereof and comprised of a mouth, a seat, and cylindrical sides therebetween, said seathaving a radial wall with an outwardly extending pocket therein and axial opening communicating between said pocket and said mouth;

c. a projectile having nose, side, and aft sections and affixed to said bore at said side section, said sections located within said bore between said first and second end portions; and i d. first and second primer means affixed respectively in said pocket of said tube seat and to said aft section of said projectile, whereby detonation of said first primer initiates a flash wave that propagates through said axial opening of said tube and said axial bore of said projectile to detonate said second primer means and whereby the detonation of said second primer means axially advances said nose section of said projectile beyond said first end portion of said propellant prior to substantial ignition of said propellant.

3. In a round of telescoped caseless ammunition:

a. a tubular propellant charge comprised of first and second end portions and an axial bore therebetween;

b. an igniter tube affixed within said bore at said first end thereof and comprised of a mouth, a seat, and cylindrical sides therebetween, said seat having a radial wall with an outwardly extending pocket therein and axial opening communicating between said pocket and said mouth;

c. a projectile having nose, side, and aft sections and affixed to said bore at said side section, said section located within said bore between said first and second end portions; and

d. first, second, and third primer means affixed respectively in said pocket of said tube seat, to said cylindrical sides of said tube between said seat and said mouth thereof, and to said aft section of said projectile, whereby detonation of said first primer means initiates a flash wave that propagates through said axial opening of said tube to detonate said second primer thereby reinforcing said flash wave and relaying it to said third primer and effecting detonation thereof and whereby the detonation of said third primer axially advances said nose sec tion of said projectile beyond said second end of said projectile prior to substantial ignition of said propellant charge.

4. In a round of telescoped caseless ammunition:

a. a tubular propellant charge comprised of first and second end portions and an axial bore therebetween;

b. an igniter tube affixed within said bore at said first end thereof and comprised ofa mouth, a seat, and cylindrical sides therebetween, said seat having a radial wall with an outwardly extending pocket therein and an axial opening communicating between said pocket and said mouth;

c. a projectile having nose and side sections and an aft section having a rearward facing cavity therein, said sections affixed to said bore at said side section and located within said bore between said first and second end portions; and

d. first and second primer means affixed respectively in said pocket of said tube seat and to said cavity in said aft section of said projectile, whereby detonation of said first primer initiates a flash wave that propagates through said axial opening of said tube and said axial bore of said projectile to detonate said second primer means and whereby the detonation of said second primer means axially advances said nose section of said projectile beyond said first end portion of said propellant prior to substantial ignition of said propellant. 

1. In a round of telescoped caseless ammunition: a. a tubular propellant charge comprised of first and second end portions and an axial bore therebetween, said first end portion having a radial wall with an outwardly extending axial pocket therein and an axial opening communicating between said pocket and said bore; b. a projectile having nose, side, and aft sections and affixed to said bore at said side section, said sections located within said bore between said first and second end portions; and c. first and second primer means affixed respectively in said pocket of said first end portion and to said aft section of said projectile, whereby detonation of said first primer initiates a flash wave that propagates through said axial opening of said pocket and said axial bore of said propellant to detonate said second primer means and whereby the detonation of said second primer means advances said nose section of said projectile beyond said first end portion of said propellant prior to substantial ignition of said propellant.
 2. In a round of telescoped caseless ammunition: a. a tubular propellant charge comprised of first and second end portions and an axial bore therebetween; b. an igniter tube affixed within said bore at said first end thereof and comprised of a mouth, a seat, and cylindrical sides therebetween, said seat having a radial wall with an outwardly extending pocket therein and axial opening communicating between said pocket and said mouth; c. a projectile having nose, side, and aft sections and affixed to said bore at said side section, said sections located within said bore between said first and second end portions; and d. first and second primer means affixed respectively in said pocket of said tube seat and to said aft section of said projectile, whereby detonation of said first primer initiates a flash wave that propagates through said axial opening of said tube and said axial bore of said projectile to detonate said second primer means and whereby the detonation of said second primer means axially advances said nose section of said projectile beyond said first end portion of said propellant prior to substantial ignition of said propellant.
 3. In a round of telescoped caseless ammunition: a. a tubular propellant charge comprised of first and second end portions and an axial bore therebetween; b. an igniter tube affixed within said bore at said first end thereof and comprised of a mouth, a seat, and cylindrical sides therebetween, said seat having a radial wall with an outwardly extending pocket therein and axial opening communicating between said pocket and said mouth; c. a projectile having nose, side, and aft sections and affixed to said bore at said side section, said section located within said bore between said first and second end portions; and d. first, second, and third primer means affixed respectively in said pocket of said tube seat, to said cylindrical sides of said tube between said seat and said mouth thereof, and to said aft section of said projectile, whereby detonation of said first primer means initiates a flash wave that propagates through said axial opening of said tube to detonate said second primer thereby reinforcing said flash wave and relaying it to said third primer and effecting detonation thereof and whereby the detonation of said third primer axially advances said nose section of said Projectile beyond said second end of said projectile prior to substantial ignition of said propellant charge.
 4. In a round of telescoped caseless ammunition: a. a tubular propellant charge comprised of first and second end portions and an axial bore therebetween; b. an igniter tube affixed within said bore at said first end thereof and comprised of a mouth, a seat, and cylindrical sides therebetween, said seat having a radial wall with an outwardly extending pocket therein and an axial opening communicating between said pocket and said mouth; c. a projectile having nose and side sections and an aft section having a rearward facing cavity therein, said sections affixed to said bore at said side section and located within said bore between said first and second end portions; and d. first and second primer means affixed respectively in said pocket of said tube seat and to said cavity in said aft section of said projectile, whereby detonation of said first primer initiates a flash wave that propagates through said axial opening of said tube and said axial bore of said projectile to detonate said second primer means and whereby the detonation of said second primer means axially advances said nose section of said projectile beyond said first end portion of said propellant prior to substantial ignition of said propellant. 